SEARCH · PubMed Health

Results for “Bioactive peptide”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 847 records · Page 47Linked to original sources

PubMed2002

Neutralization of adrenomedullin inhibits the growth of human glioblastoma cell lines in vitro and suppresses tumor xenograft growth in vivo.

Presently, there is no effective treatment for glioblastoma, the most malignant and common brain tumor. Growth factors are potential targets for therapeutic strategies because they are essential for tumor growth and progression. Peptidylglycine alpha-amidating monooxygenase is the enzyme producing alpha-amidated bioactive peptides from their inactive glycine-extended precursors. The high expression of peptidylglycine alpha-amidating monooxygenase mRNA in glioblastoma and glioma cell lines points to the involvement of alpha-amidated peptides in tumorigenic growth processes in the brain. After screening of amidated peptides, it was found that human glioblastoma cell lines express high levels of adrenomedullin (AM) mRNA, and that immunoreactive AM is released into the culture medium. AM is a multifunctional regulatory peptide with mitogenic and angiogenic capabilities among others. Real-time quantitative reverse transcriptase-polymerase chain reaction analysis showed that AM mRNA was correlated to the tumor type and grade, with high expression in all glioblastomas analyzed, whereas a low expression was found in anaplastic astrocytomas and barely detectable levels in low-grade astrocytomas and oligodendrogliomas. In the present study we also demonstrate the presence of mRNA encoding the putative AM receptors, calcitonin receptor-like receptor/receptor activity-modifying protein-2 and -3 (CRLR/RAMP2; CRLR/RAMP3) in both glioma tissues and glioblastoma cell lines and further show that exogenously added AM can stimulate the growth of these glioblastoma cells in vitro. These findings suggest that AM may function as an autocrine growth factor for glioblastoma cells. One way to test the autocrine hypothesis is to interrupt the function of the endogenously produced AM. Herein, we demonstrate that a polyclonal antibody specific to AM, blocks the binding of the hormone to its cellular receptors and decreases by 33% (P < 0.001) the growth of U87 glioblastoma cells in vitro. Intratumoral administration of the anti-AM antibody resulted in a 70% (P < 0.001) reduction in subcutaneous U87 xenograft weight 21 days after treatment. Furthermore, the density of vessels was decreased in the antibody-treated tumors. These findings support that AM may function as a potent autocrine/paracrine growth factor for human glioblastomas and demonstrate that inhibition of the action of AM (produced by tumor cells) may suppress tumor growth in vivo.

Adrenomedullin↗

PubMed2000

Endothelin receptor pathway in human left ventricular myocytes: relation to contractility.

BACKGROUND: Increased synthesis and release of the potent bioactive peptide endothelin-1 (ET-1) occurs during and after cardiac surgery. However, the cellular and molecular basis for the effects of ET-1 on human left ventricular (LV) myocyte contractility remains unknown. METHODS: LV myocyte contractility was examined from myocardial biopsies taken from patients (n = 30) undergoing elective coronary artery bypass. LV myocytes (n = 997, > 30/patient) were isolated using microtrituration and contractility examined by videomicroscopy at baseline and after ET-1 exposure (200 pmol/L). In additional studies, myocytes were pretreated to inhibit either protein kinase C (PKC) (chelerythrine, 1 micromol/L), the sodium/hydrogen (Na/H) exchanger (EIPA, 1 micromol/L), both PKC and the Na/H exchanger, or the ET(A) receptor (BQ-123, 1 micromol/L), followed with ET-1 exposure. RESULTS: Basal myocyte shortening increased 37.8 +/- 6.3% with ET-1 (p < 0.05). Na/H exchanger, PKC, and dual inhibition all eliminated the effects of ET-1. Furthermore, ET(A) inhibition demonstrated that ET-1 effects on myocyte contractility were mediated through the ET(A) receptor subtype. CONCLUSIONS: ET-1 directly influences human LV myocyte contractility, which is mediated through the ET(A) receptor and requires intracellular activation of PKC and stimulation of the Na/H exchanger.

Cells, Cultured↗

PubMed1987

A membrane-bound, calcium-dependent protease in yeast alpha-cell cleaving on the carboxyl side of paired basic residues.

Paired basic residues are known as a typical site for proteolytic processing of precursors of bioactive peptides. By using a fluorogenic substrate Boc-Gln-Arg-Arg-MCA, a unique endoprotease exhibiting hydrolytic specificity toward the carboxyl side of paired basic residues was partially purified (about 4600-fold) from the membrane fraction of yeast Saccharomyces cerevisiae alpha-cells. The enzyme is a calcium-dependent thiol protease, with optimal pH at 7.0. It is a glycoprotein, with an apparent molecular weight of about 100,000-120,000. It cleaves fluorogenic substrates and a synthetic model peptide at the carboxyl side of paired basic residues. From its unique substrate specificity, this enzyme may be involved in precursor processing in vivo.

Calcium↗

PubMed1987

Purification and characterization of an aminopeptidase from bovine cornea.

An aminopeptidase from bovine cornea has been extensively purified by gel filtration and ion-exchange chromatography. The purified enzyme with a molecular weight of 96,000 showed broad substrate specificity. All of the various aminoacyl bonds were hydrolyzed optimally at pH 6.5. The purified enzyme showed hydrolytic activity towards bioactive peptides such as enkephalins, bradykinin, and angiotensin-II. The enzyme was inhibited by bestatin, amastatin, puromycin, bacitracin, sulfhydryl reagents and metal chelators. Only Co2+ stimulated the enzyme whereas other heavy metal ions were toxic. The gross properties of the corneal enzyme resemble those of an aminopeptidase III isolated from bovine lens.

Aminopeptidases↗

PubMed2002

Processing of proendothelin-1 by members of the subtilisin-like pro-protein convertase family.

Endothelial cells (ECs) secrete numerous bioactive peptides that are initially synthesized as inactive precursor proteins. One of these, proendothelin-1 (proET-1), undergoes proteolysis at specific pairs of basic amino acids. Here, we wished to examine the role of mammalian convertases in this event. Northern blot analysis shows that only furin and PC7 are expressed in ECs. In vitro cleavage of proET-1 by furin or PC7 demonstrated that both enzymes efficiently and specifically process proET-1. These data reveal that furin and PC7 have similar specificities towards proET-1 and suggest that both enzymes may participate in the maturation of proET-1 in ECs.

Animals↗

PubMed1997

A simple and rapid procedure for the purification of synthetic polypeptides by a combination of affinity chromatography and methionine chemistry.

Chemical synthesis of bioactive peptides has become a widespread and rapidly growing technique due to automated and efficient protocols for chain assembly. For most applications, the crude synthetic product must be purified to remove residual reactants, failure sequences and chemically modified peptide species. We propose here a method of universal applicability based on immobilized metal ion affinity chromatography, CNBr cleavage and use of reversible Met-sulfoxide protection. With this method we were able to purify to homogeneity in high yield the PbCS 242-310 polypeptide corresponding to the C-terminal region of Plasmodium berghei CS protein.

Amino Acid Sequence↗

PubMed1998

Residues unique to the pro-hormone convertase PC2 modulate its autoactivation, binding to 7B2 and enzymatic activity.

The prohormone convertase PC2 is one of the major subtilisin/kexin-like enzymes responsible for the formation of small bioactive peptides in neural and endocrine cells. This convertase is unique among the members of the subtilisin/kexin-like mammalian serine proteinase family in that it undergoes zymogen processing of its inactive precursor proPC2 late along the secretory pathway and requires the help of a PC2-specific binding protein known as 7B2. We hypothesized that some of these unique properties of PC2 are dictated by the presence of PC2-specific amino acids, which in the six other known mammalian convertases are otherwise conserved but distinct. Accordingly, six sites were identified within the catalytic segment of PC2. Herein we report on the site-directed mutagenesis of Tyr194 and of the oxyanion hole Asp309 and the consequences of such mutations on the cellular expression and enzyme activity of PC2. The data show that the Y194D mutation markedly increases the ex vivo ability of PC2 to process proopiomelanocortin (POMC) into beta-endorphin in cells devoid of 7B2, e.g. BSC40 cells. In these cells, expression of native PC2 does not result in the secretion of measurable in vitro activity against a pentapeptide fluorogenic substrate. In contrast, secreted Y194D-PC2 exhibited significant enzymatic activity, even in the absence of 7B2. Based on co-immunoprecipitations and Western blots, binding assays indicate that Tyr194 participates in the interaction of PC2 with 7B2, and that the oxyanion hole Asp309 is critical for the binding of proPC2 with pro7B2.

Animals↗

PubMed2004

The effect of PACAP on rhythmic melatonin release of avian pineals.

Pituitary adenylate cyclase activating polypeptide (PACAP) is a ubiquitous member of the VIP/secretin/glucagon bioactive peptide family. The distribution, concentration of PACAP, and its role in the control of rhythmic melatonin (MT) secretion from chicken pineal gland were studied. In the chicken pineal gland (ChPG), 40ng PACAP/g tissue was measured with radioimmunoassay. No midday-midnight differences in the PACAP content of the ChPG could be detected. Immunohistochemical studies of ChPG showed PACAP immunoreactive nerve fibers in the perivascular space and around the pinealocytes. Neither PACAP-labeled perikarya nor PACAP immunopositivity in the pinealocytes could be detected. In five day perifusion experiments, carried out under darkness, both MT and cAMP showed circadian rhythmic release pattern from explanted ChPG. One hour exposure of ChPG to PACAP induced transient (3-4h) elevation of MT and cAMP release. The responses were dose-dependent in the range from 1 to 100nM PACAP concentrations. The magnitude of the response was independent on the phase of the daily cycle in which PACAP was applied. cAMP levels during normal daily cycle and also PACAP-induced cAMP responses always preceded similar changes of MT by about an hour suggesting that cAMP is an intracellular intermediate in controlling MT release from the ChPG. At the same time PACAP, similarly to VIP, did not shift the phase of the in vitro circadian MT rhythm of the pineals. Our data reveal, that PACAP is present in nerve fibers in the chicken pineals and pineal cells contain functioning PACAP-sensitive receptors. PACAP apparently exerts a modulatory effect of the rhythmic MT release from the chicken pineal but does not modify the intrinsic biological clock in the avian pineal gland. Thus, cAMP-mediated intracellular mechanisms in ChPG are not components of the pineal circadian clock, but intermediaries between the clock-mechanism and MT release and may also be components of clock-independent MT release modifiers.

Animals↗

PubMed2003

The role of melanocortins and their receptors in inflammatory processes, nerve regeneration and nociception.

The melanocortins are a family of bioactive peptides derived from proopiomelanocortin. Those peptides, included among hormones and comprising ACTH, alpha-MSH, beta-MSH and gamma-MSH, are best known mainly for their physiological effects, such as the control of skin pigmentation by alpha-MSH, and ACTH effects on pigmentation and steroidogenesis. Melanocortins are released in various sites in the central nervous system and in peripheral tissues, and participate in the regulation of multiple physiological functions. They are involved in grooming behavior, food intake and thermoregulation processes, and can also modulate the response of the immune system in inflammatory states. Research of the past decade provided evidence that melanocortins could elicit their diverse biological effects by binding to a distinct family of G protein-coupled receptors with seven transmembrane domains. To date, five melanocortin receptor genes have been cloned and characterized. Those receptors differ in their tissue distribution and in their ability to recognize various melanocortins. These advances have opened up new horizons for exploring the significance of melanocortins, their ligands and their receptors for a variety of important physiological functions. We reviewed the origin of MSH peptides, the function and distribution of melanocortin receptors and their endogenous and exogenous ligands and the role of melanocortins and their receptors in inflammatory processes, nerve regeneration and nociception. Moreover, we analyzed their interaction with opioid peptides and finally, we discussed the postulated role of the melanocortin system in pain transmission at the spinal cord level.

Amino Acid Sequence↗

PubMed2003

Characterization of tachykinin NK2 receptor in the anterior pituitary gland.

Tachykinins are a family of bioactive peptides that interact with three subtypes of receptors: NK1, NK2 and NK3. Substance P has greater affinity for NK1, and neurokinin A (NKA) for NK2 receptor subtype. Although only NK1 receptor has been characterized in the anterior pituitary gland, some evidence suggests the existence of NK2 receptors in this gland. Therefore, we investigated the presence of NK2 receptors in the anterior pituitary gland of male rats by radioligand binding studies using labeled SR48968, a non peptidic specific antagonist. [3H]SR48968 specific binding to cultured anterior pituitary cells was time-dependent and saturable, but with a lower affinity than previously reported values for cells expressing NK2 receptors. Unlabeled NKA inhibited only partially [(3)H]SR48968 specific binding to whole anterior pituitary cells. Since SR48968 is a non polar molecule, we performed experiments to discriminate surface from intracellular binding sites. SR48968 exhibited both surface and intracellular specific binding. Analysis of the surface-bound ligand indicated that [3H]SR48968 binds to one class of receptor with high affinity. Neurokinin A completely displaced [3H]SR48968 surface specific binding fitting to a two-site/two-state model with high and low affinity. Additionally, immunocytochemical studies showed that the NK2 receptor is expressed at least in a subset of lactotropes. These results demonstrate the presence of NK2 receptors in the anterior pituitary gland and suggest that NKA actions in this gland are mediated, at least in part, by the NK2 receptor subtype.

Animals↗

PubMed1999

Decreased expression of angiotensin-converting enzyme in the airway epithelium of asthmatic subjects is associated with eosinophil inflammation.

BACKGROUND: Angiotensin-converting enzyme (ACE) is a peptidase involved in the metabolism of several bioactive peptides. It may be involved in the airway inflammation and hyperresponsiveness that occur in asthma. OBJECTIVE: We studied the expression of ACE in the airway mucosa of normal and asthmatic subjects and assessed the relationship between ACE expression and airway inflammation and bronchial hyperresponsiveness in asthma. METHODS: We used immunohistochemistry to study the ACE expression and airway inflammation in bronchial biopsy samples obtained by fiberoptic bronchoscopy from 20 asthmatic subjects randomly assigned to groups treated with (n = 10) or without inhaled corticosteroids (n = 10) and from normal subjects (n = 10). Airway response to methacholine and bradykinin was also determined for all subjects. RESULTS: In normal subjects ACE was present in the surface epithelium, the endothelial cells of the lamina propria, and the submucosal glands, in which ACE was found in seromucous cells and in secreted mucus. ACE was not detected in smooth muscle cells and in most of the endothelial cells of the vascular network surrounding the glands. ACE was absent or present at lower levels in the surface epithelium of asthmatic subjects not treated with corticosteroids compared with those treated with corticosteroids and the control group. In asthmatic subjects low levels of ACE in the epithelium were associated with larger numbers of eosinophils in the epithelium and lamina propria. There was no relationship between ACE levels in the airway mucosa and airway responsiveness to methacholine and bradykinin. CONCLUSION: ACE expression is decreased in the epithelium of asthmatic patients and is associated with increased eosinophil inflammation.

Asthma↗

PubMed2000

A highly sensitive and selective radioimmunoassay for the measurement of neurotensin.

A highly selective and sensitive radioimmunoassay (RIA) for the detection of endogenous neurotensin (NT) has been developed. We have raised a C-terminally-directed antibody (CAb) that specifically binds 'biologically active' NT (NT and NT(8-13)) and that does not significantly cross-react with inactive NT metabolites or other bioactive peptides in the CNS. By reducing the volume of the assay to a low volume-RIA (30 microl), such that in vivo measurements can be made, we have increased the sensitivity (<0.3 fmol per tube), with inter- and intra-assay variations of 11.2 and 5.8%, respectively. Comparisons with similar methods of detecting NT have demonstrated that this RIA has a higher sensitivity than previously used RIA's and ELISA's. The data presented suggests that this sensitive RIA is a reliable method ideal for the detection of small quantities of biologically active NT.

Animals↗

PubMed1997

Involvement of cholinergic processes in cholecystokinin (CCK) release [corrected] by luminal oleic acid.

Cholecystokinin (CCK) is an important bioactive peptide that stimulates pancreatic enzyme secretion. Circulating CCK is secreted from endocrine cells in the upper small intestine in response to various luminal stimuli and to vascular administration of gastrin releasing peptides. However, the mechanism of its release has not been fully elucidated. In the present study, the vascularly perfused duodenojejunum was isolated from male Wistar rats. The effects of luminal infusion of sodium oleate (2 or 0.4%) or intra-arterial infusion of neuromedin C(10(-7) M) with or without atropine and with a recently synthesized specific bombesin antagonist (EABI) were examined. The CCK release produced by intra-arterial infusion of neuromedin C was inhibited by EABI in a dose-dependent manner. The CCK release produced by luminal sodium oleate was inhibited by atropine, but not affected by EABI. The CCK release stimulated by luminal sodium oleate is mediated, at least in part, by a cholinergic mechanism, but neuromedin C directly stimulates CCK release via its receptor on CCK-producing cells.

Animals↗

PubMed2000

Conversion and storage of somatostatin are established before response to secretagogue stimuli in P19 neurons.

In mature neurons, neuropeptides are synthesized via limited proteolysis of propolypeptides by convertases. The bioactive peptides are then stored in secretory granules until they are released extracellularly upon the induction of a fusion between granules and the plasma membrane, in response to secretagogues. We used the mouse P19 embryonic carcinoma cells as a model to determine if the capacities to convert and store neuropeptides and to secrete them in a regulated fashion are established coordinately during neuronal differentiation. We have previously shown that both undifferentiated P19 cells and their neuronal derivatives express the largely distributed furin, PACE4 and PC5 convertases, whereas only neuronal derivatives express the neuroendocrine convertase PC2. In addition, undifferentiated cells displayed furin- rather than PC2-like converting capacities. The present work demonstrates that day 8 P19 neurons mainly convert prosomatostatin (proSS) to somatostatin-14 (SS-14) using HPLC and radioimmunoassay (RIA) analyses, indicating that P19 cells acquire PC2-like converting capacities as a consequence of neuronal differentiation. SS-14 was predominantly intracellular in neuronal cells which were shown to express several granins, markers of granules, by Western blotting. However, cell membrane depolarization with 50 mM K+, a general secretagogue stimulus, evoked the release of SS-14 by day 12, but not by day 8, P19 neurons. The results thus demonstrate that capacities to convert and store neuropeptides can be established before coupling of stimulus-secretion during neuronal differentiation.

1-Methyl-3-isobutylxanthine↗

PubMed2001

Covalently conjugated VEGF--fibrin matrices for endothelialization.

Vascular endothelial growth factor (VEGF) is a key factor in endothelial cell biology and blood vessel formation and a candidate therapeutic for the stimulation of angiogenesis-dependent tissue regeneration. The objective of this study was to confer the angiogenic activity of VEGF(121) upon the biomaterial fibrin, a natural substrate for endothelial cell growth and clinically accepted as 'fibrin glue'. To achieve this, we engineered fibrin-based hydrogels that were covalently modified with VEGF(121). Our laboratory has recently developed novel methodology that allows the covalent incorporation of exogenous bioactive peptides by the transglutaminase activity of factor XIIIa into fibrin during coagulation. Here, this ability of factor XIIIa to crosslink additional proteins within fibrin was employed to covalently incorporate VEGF(121). By recombinant DNA methodology, a mutant VEGF(121) variant, alpha(2)-PI(1--8)-VEGF(121), which contains an additional factor XIIIa substrate sequence NQEQVSPL at the aminoterminus, was expressed in E. coli. In soluble form, the mutant protein fully retained its mitogenic activity for endothelial cells. Using (125)I-labeled alpha(2)-PI(1--8)-VEGF(121), its covalent incorporation and the efficiency of incorporation into fibrin was demonstrated and characterized. The immobilized, fibrin-conjugated VEGF(121) protein remained an active and very efficient mitogen for human endothelial cells grown on two-dimensional VEGF(121)-modified fibrin surfaces, and the incorporation of increasing amounts of alpha(2)-PI(1--8)-VEGF(121) resulted in dose-dependent enhancement of endothelial cell growth. The VEGF-modified fibrin matrices can be formed as injectable gels in a single-step reaction under physiological conditions in vivo. When used as a ingrowth matrix, such VEGF incorporating materials could be useful in a variety of clinical situations that require an angiogenic response into an ischemic region or inplant.

Cell Division↗

PubMed2003

Relation of beta-casomorphin to apnea in sudden infant death syndrome.

Sudden infant death syndrome (SIDS) is the most common cause of death in infants and its pathogenesis is complex and multifactorial. The aim of this review is to summarize recent novel findings regarding the possible association of beta-casomorphin (beta-CM) to apnea in SIDS, which has not been widely appreciated by pediatricians and scientists. beta-CM is an exogenous bioactive peptide derived from casein, a major protein in milk and milk products, which has opioid activity. Mechanistically, circulation of this peptide into the infant's immature central nervous system might inhibit the respiratory center in the brainstem leading to apnea and death. This paper will review the possible relationship between beta-CM and SIDS in the context of passage of beta-CM through the gastrointestinal tract and the blood-brain barrier (BBB), permeability of the BBB to peptides in infants, and characterization of the casomorphin system in the brain.

Animals↗

PubMed1997

Cyclic AMP and sympathetic neuronal programmed cell death.

The survival and proper functioning of sympathetic neurons are dependent on nerve growth factor (NGF). When immature sympathetic neurons are deprived of NGF, they undergo an 'active' dying process usually termed 'programmed cell death' or 'apoptosis'. This trophic factor dependence is age-related such that the cells become less dependent on NGF as they mature. Removal of NGF in immature cultures, which triggered the process of programmed cell death, resulted in a significant decrease of intracellular cAMP levels. In contrast, when these cells matured in culture and became relatively NGF independent, NGF withdrawal did not lead to a drop of cAMP levels. Pituitary adenylate cyclase-activating polypeptide (PACAP), a naturally occurring bioactive peptide structurally similar to VIP, could increase cAMP levels in these sympathetic neurons, and delay neuronal cell death resulting from NGF deprivation. These results suggest that PACAP may serve as a neurotrophic factor in sympathetic neurons.

Animals↗

PubMed1992

Autologous facial fat transplantation: improved graft maintenance by microbead bioactivation.

An alternative approach to the management of free fat transplantation resorption was evaluated in a rat facial model. Fat grafts obtained from the inguinal region were transferred to subcutaneous lateral facial sites in 20 animals. The grafts were mixed with either basic fibroblast growth factor (bFGF) alone or dextran beads that had been pretreated with bFGF. The grafts were then compared by weight and histology at 1 and 6 months postoperatively. Although graft weights were nearly comparable at 1 month, substantial differences were seen at 6 months, with the bead-containing grafts exhibiting near complete weight maintenance and better overall graft form. Histologically, the bead-containing grafts had extensive intercellular collagen formation and a heterogeneity of adipocyte cell sizes, particularly after 1 month. These findings suggest that the addition of cell-specific bioactive peptides that affect either the preadipocyte cell line and/or the fibroblastic components of the recipient site improve postoperative fat graft weight maintenance. Delivery of the biochemical agent appears to require a carrier system to exert its effects.

Adipose Tissue↗